An integrated circuit in a computer is used for displaying some data signals such as images on the screen of said computer for example, said data signals comprising data samples that are pixels in this case. An image usually comprises 1280*1024 pixels and a pixel is usually defined by thirty-two bits. This leads to about forty million bits to be transferred onto the screen for an image. To avoid transferring so many data, a solution is proposed and described in the U.S. Pat. No. 5,862,150 referenced “Video Frame Signature Capture”.
It consists in using a random access memory digital to analog converter also called RAMDAC that comprises a signature generator, a central processing unit CPU and a digital bus. The computer comprises a frame buffer that contains an image to be displayed on the screen. The RAMDAC permits to compute a signature on the image that is the frame buffer and to compare the result to a “good signature” and this by means of the signature generator, the central processing unit CPU and the digital bus.
One drawback of such solution is that it does not test the images in real time. Indeed, the RAMDAC takes the pixels from the frame buffer, which describes a fixed image to be displayed on the screen of the computer. Thus, when the images displayed on the screen of the computer are images of a video film for example, one does not test the integrated circuit in its functional environment, i.e. the images of a video film as soon as they are displayed on the screen of the computer. Moreover, a central processing unit CPU is needed to compute the signature and this solution is only specific to a RAMDAC. The central processing unit CPU leads to a high consumption and to the use of software.